Berms are raised mounds on contour or slightly off. You can make berms with logs or rocks or other materials. Berms often come with swales, but there are specific reasons to use berms without swales, such as protecting an area from runoff and sending it elsewhere (in which case you may want it slightly off contour).
Fishscale berms have many names, but they do resemble fish scales. They are small triangular or half moon berms around individual trees that help direct and hold water around that tree. Trees should be staggered in a tessellation pattern when using this water catchment method as it increases the water flowing to each tree. Risk from blowouts caused by too much water at once are minimal.
With sand, erosion can be a problem. We use logs, limerock, or other infrastructure to hold these in place if the slope is steep. Otherwise, we just use chop and drop or ground cover planted on the berm to reduce erosion. Note: even on “flat” land there is usually a slope that can be utilized to direct water.
This is one of our favorite water catchment methods on our somewhat hilly sand dune farm in central Florida. It’s a good way to concentrate the water right where you need it, and we build it while planting the tree by putting any extra sand on the downslope in this “V” shape and adding wood chips or logs. There are many versions of this pattern. A common one is a Net and Pan (see next Section).
Fish scale berms.
Above is a living solution that works great in sand or other eroded areas. Vetiver grass is effective even on very steep slopes such as some of the heavily eroded slopes in Haiti, but also works well in Florida. Fakahatchee grass is a native plant in Florida that is a great chop and drop and nutrient collector as well. One could plant Fakahatchee or vetiver on contour on a slope instead of digging a swale. We’re experimenting with that on our farm currently.
Whatever you use as a living berm should not aggressively spread through rhizomes or roots (to avoid weeding), should be deep rooted, and should not need a lot of nutrition. Nature creates these water and nutrient traps on hill sides with fallen branches that leaves collect on, and in other ways.
Use your imagination!